Tanuki65....

Thank you for your email.  

I actually have two logic boards for my Color Classic.  One is a Color Classic II logic board which I am running now.  The second logic board I have is a 575.  I am attempting the Mystic upgrade to it now.  However, I am at a stand still as I am unable to find any 70 ns 512K 68 pin VRAM SIMMs

I suspect when everything is all finished, I will be running the 575 in my Color Classic, and have the Color Classic II logic board as a back up.

I have never heard of 7.5.4!!  I will start looking for it along with Baton Mail.

Thank you for your help.

jack